Python3中hasattr()、getattr()、setattr()、delattr()函数及示例代码

hasattr()函数

hasattr()函数用于判断是否包含对应的属性

语法：

hasattr(object,name)

参数：

object--对象

name--字符串，属性名

返回值：

如果对象有该属性返回True，否则返回False

示例：

class People:
  country='China'
  def __init__(self,name):
    self.name=name
  def people_info(self):
    print('%s is xxx' %(self.name))
obj=People('aaa')
print(hasattr(People,'country'))
#返回值：True
print('country' in People.__dict__)
#返回值：True
print(hasattr(obj,'people_info'))
#返回值：True
print(People.__dict__)
##{'__module__': '__main__', 'country': 'China', '__init__': <function People.__init__ at 0x1006d5620>, 'people_info': <function People.people_info at 0x10205d1e0>, '__dict__': <attribute '__dict__' of 'People' objects>, '__weakref__': <attribute '__weakref__' of 'People' objects>, '__doc__': None}

getattr()函数

描述：

getattr()函数用于返回一个对象属性值

语法：

getattr(object,name,default)

参数：

object--对象

name--字符串，对象属性

default--默认返回值，如果不提供该参数，在没有对于属性时，将触发AttributeError。

返回值：

返回对象属性值

class People:
  country='China'
  def __init__(self,name):
    self.name=name

  def people_info(self):
    print('%s is xxx' %(self.name))
obj=getattr(People,'country')
print(obj)
#返回值China
#obj=getattr(People,'countryaaaaaa')
#print(obj)
#报错
# File "/getattr()函数.py", line 32, in <module>
#   obj=getattr(People,'countryaaaaaa')
# AttributeError: type object 'People' has no attribute 'countryaaaaaa'
obj=getattr(People,'countryaaaaaa',None)
print(obj)
#返回值None

setattr()函数

描述：

setattr函数，用于设置属性值，该属性必须存在

语法：

setattr(object,name,value)

参数：

object--对象

name--字符串，对象属性

value--属性值

返回值：

无

class People:
  country='China'
  def __init__(self,name):
    self.name=name
  def people_info(self):
    print('%s is xxx' %(self.name))
obj=People('aaa')
setattr(People,'x',111) #等同于People.x=111
print(People.x)
#obj.age=18
setattr(obj,'age',18)
print(obj.__dict__)
#{'name': 'aaa', 'age': 18}
print(People.__dict__)
#{'__module__': '__main__', 'country': 'China', '__init__': <function People.__init__ at 0x1007d5620>, 'people_info': <function People.people_info at 0x10215d1e0>, '__dict__': <attribute '__dict__' of 'People' objects>, '__weakref__': <attribute '__weakref__' of 'People' objects>, '__doc__': None, 'x': 111}

delattr()函数

描述：

delattr函数用于删除属性

delattr(x,'foobar)相当于del x.foobar

语法：

setattr(object,name)

参数：

object--对象

name--必须是对象的属性

返回值：

无

示例：

class People:
  country='China'
  def __init__(self,name):
    self.name=name
  def people_info(self):
    print('%s is xxx' %(self.name))
delattr(People,'country') #等同于del People.country
print(People.__dict__)
{'__module__': '__main__', '__init__': <function People.__init__ at 0x1006d5620>, 'people_info': <function People.people_info at 0x10073d1e0>, '__dict__': <attribute '__dict__' of 'People' objects>, '__weakref__': <attribute '__weakref__' of 'People' objects>, '__doc__': None}

补充示例：

class Foo:
  def run(self):
    while True:
      cmd=input('cmd>>: ').strip()
      if hasattr(self,cmd):
        func=getattr(self,cmd)
        func()
  def download(self):
    print('download....')
  def upload(self):
    print('upload...')
# obj=Foo()
# obj.run()

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